<%= simple_form_for(@task, html:{class: "form-signin"}) do |f| %>
  <%= f.error_notification %>
<%= f.input :content, label: false, required: true, autofocus: true, input_html:{class: "form-control"}, placeholder: "任务内容"%>
    <%= f.button :submit, class: "btn btn-primary btn-block" %>
<% end %>
